Fig 6.

Schematic representation of the principal signalling networks and transcription factors regulating osteoblast differentiation and osteogenesis (see text for details). Lines with arrowheads indicate a positive action, lines with bars indicate an inhibition and dashed lines indicate that function has to be proven. The lineage commitment and the differentiation of cultured MSC are signed by the acquisition of specific osteoblast functions. In boxes are shown genes that are significantly up-regulated during osteogenic differentiation of MSC. The ‘Gene Ontology Annotation’ of genes listed here is associated to GF-signalling pathways, cell communication and skeletal development. The up-regulated genes have been grouped according to the differentiation status of cultured MSC: ‘Pre-osteoblasts’ are MSC which are able to produce ALP (cytochemical activity, ×10) and generate ‘Colony Forming Units’; ‘Differentiated osteoblasts’ are cells which have the competence to deposit mineral nodules in vitro (von Kossa staining, ×10). Genes are reported with the official symbol, as shown in ‘Gene’ database (http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene).